rotten apple

apple of someone's eye

The object of somebody's affections; a person (or sometimes a thing) that someone strongly prefers; a favorite, a loved one.

apple polisher

A sycophant; a toady.

bad apple

A person who is not wholesome, honest, or trustworthy, especially one who has an adverse influence on others.

rotten egg

A person who is the latest, the last, or the slowest in a group to arrive somewhere or to perform a certain task.

something is rotten in the state of Denmark

Something is not right, seriously amiss, especially when leading to suspicion of motive.

spoil somebody rotten

Alternative form of spoil someone rotten.

spoil someone rotten

To overindulge someone, especially when it results in making them selfish and demanding.

the apple does not fall far from the tree

A child grows up to be similar to its parents, both in behavior and in physical characteristics.